Thermal overload release



y 1934. v. 1 DARNELL ET AL 1,966,926

' THERMAL OVERLOAD RELEASE Filed June 8, 1932 2 Sheets-Sheet l July 17, 1934. v. 1.. DARNELL ET AL THERMAL OVERLOAD RELEASE 2 Sheets-Sheet 2 Filed June 8, 1932 Patented July 17, 1934 UNITED STATES PATENT OFFICE 1,900,920 I 'rnsamu. OVEBLOAD amass Application June a, 1932, Serial a... 616,064

:0 Claims. (61200-124) This invention relates to electric switch operating means, and more particularly to automatic means for actuating a switch under abnormal operating conditions, which switch is otherwise subject to manual operation freely into on and oil positions independently of the automatic operating means.

For illustrative purposes,'the present invention is herein shown and described as applied to a make and break switch of the snap-over type which may be manually shifted into on and oil positions, with which is associated a spring actuated device normally held inoperative by a fusible detent connection, which when released by-an abnormal rise of temperature, actuates the switch independently of the manual actuating means. While the switch is shown and will be described as being automatically actuated from on to off position, it will be obvious that this relationmight be reversed and the switch caused to automatically operate from oil to on position, and while the apparatus is primarily designed for thermal control whereby it will automatically actuate the switch in the event of overload on an electric line whereby abnormal heat is developed, it is to be understood that the operator mechanism is subject to control by pressure means or other change of operating conditions.

The object of the invention is to simplify the construction as well as the means and mode of operation of automatic switch actuating mechanism, whereby it will not only be cheapened in construction, but will be more efllcient in use, positive in action, uniform in operation, and unlikely to get out of repair.

A further object of the invention is to provide a switch operating mechanism which will be of compact form embodying few operating parts and which will be quickly responsive to a change of operating conditions.

'A further object of the invention is to provide a switch actuating mechanism which will be normally inoperative and which will not interfere with normal manual to and fro operation of the switch, but which will quickly and automatically disconnect the manual actuating means and eflfect a reversal of the switch mechanism wholLv independent thereof.

A further object of the invention is to provide a switch operating mechanism which will automatically prevent a return of the switch until the automatic mechanism has been reset for succeeding operations.

A further object of the invention is to provide an automatic mechanism which may be reset without subjecting the switch parts to unusual strain or harm.

With the above primary and other incidental objects in view, as will more fully appear in the specification, the invention consists of the features of construction, the parts and combinations thereof, and the mode of operation, or their equivalents, as hereinafter described and set forth in the claims.

Referring to the accompanying drawings, wherein is shown the preferred but obviously not necessarily the only forms of the embodiment of the invention, Fig. 1 is a side elevation of the switch and actuating mechanism therefor, the housing being shown in section. Fig. 2 is a top plan view thereof. Fig. 3 is a perspective view of the switch actuating parts removed from the housing. Fig. 4 is a perspective view of the automatic tripping means. Fig. 5 is a transverse sectional view. Fig. 6 is a side elevation and Fig. 7 a top plan view illustrating a modification of the switch operating mechanism shown in the preceding flgure. Fig. 8 is a detail view of the operator parts of the constructions shown in Figs. 5 and 6. I

Like parts are indicated by similar characters of reference throughout the several views.

Referring to the drawings, 1 is the housing or casing within the lower portion of which is gnounted a make and break switch 2 of the snapover type which comprises contact arms 3 and 4 mounted for oscillatory movement about the center 5 into and out of electrical contacting engagement with contact terminals '7 and 8. A portion of the switch mechanism is supported upon a plate 9 secured within the housing 1 and is actuated to and fro about the center 5 by the oscillatory switch arm 10. The particular switch mechanism forms no part, per se, of the present invention and has not been illustrated in detail. The actuating mechanism forming the subject matter hereof, is applicable to any switch having a to and fro actuating member corresponding to the switch arm 10 which is to be shifted to and fro to alternate the switch device. Pivotally mounted in the top of the housing 1 is a rock shaft 11 extending beyond the housing 1 and provided at its extremity with a lever, knob, or, as shown in the drawings, a crank arm 12 by which the rock shaft 11 may be manually moved to and fro. Loosely joumaled upon the rock shaft 11 is an operator arm 13, which, in the present instance, is substantialhr channel shaped to afford a recess within which the extremity of the switch arm 10 extends with the operator arm 13 projecting on opposite sides therof so that as the operator arm 13 is oscillated it will carry the switch arm 10 with it in first one direction and then in the other. A helical spring 14 coiled about the shaft 11 with one extremity connected with the shaft 11 and the other extremity engaging with the operator arm 13 tends to oscillate the operator arm 13 about the shaft 11 and independently thereof in the direction in which it is desired it shift the switch arm 10. In the present instance for illustrative purposes, the spring 14 is arranged to oscillate the operator arm 13 independently of the shaft 11 in such direction that the switch 2 will be shifted from on to off position. It will be obvious, however, that by merely reversing the switch2, the same movement of the operator arm 13 would serve to actuate the switch from off to on position.

Fixedly secured upon the rock shaft 11 adjacent to the operator arm 13 is a rock arm 15 to which is secured a spring blade or detent arm 16. This spring detent 16 is provided with a beveled lip or shoulder 17 engageable with the operator arm 13 to hold the operator arm in its retracted position. against the tension of the spring 14. The beveled lips function as a cam surface engaging. the operator 13. Thus the rock shaft 11, the operator arm 13, spring 14 and detent arm 16 with its latch 17 are interconnected into an oscillatory unit operable to and fro manually by the crank arm 12-to actuate the switch arm 10 and effect opening of. the switch 2. In such manual operation, the shaft 11 and operator arm 13 co-operate as though they were rigidly and fixedly interconnected with each other for unison movement. It would .be apparent, however, that when the switch is in its .on position, if the latch shoulder 17 is withdrawn from engagement with the operatorarm 13 by flexing the spring blade 16, the operator arm 13 willbe free to swing independently of the shaft 11 under influence of the spring 14 and thereby automatically reverse the switch, leaving the shaft 11 with its crank arm 12 and detentarm 15 carrying the latch blade 16 in their former positions.

To effect such disengagement of the latch blade 16 from the operator arm 13,.there is provided, in suitable hearings in thehousing 1, a reciprocatory rod 18 carrying a laterally projecting contact finger, 19, which extends into overlapping relation with the extremity of the spring latch blade 16 as is best shown in Fig.. 2. A helical spring 20 surrounding the reciprocatory rod 18 tends to force the rod 18 longitudinally and thereby press the projecting contact finger 19 against the latch spring 16 to withdrawthe stop shoulder 17 from engagement with the operator arm 13. The contact finger 19 extends about the rod 18 to which it is pinned by the cotter pin 21 and projects thence downwardly at 22 forming a downwardly projecting extension or finger to which is attached a hook shaped spring arm or pawl 24 which moves to and fro in unison with the reciprocator-y rod 18 and contact release finger 19. I

Mounted in a suitable block 25 of insulating material supported withinthe housing is a post or stem 26 of heatconductive material to which is attached by solder, wax, or other fusible material, a corrugated or ratchet like head 27 capable of rotation upon the stem .26 when the fusible union is broken. The hook shaped ex-- tremi sy of the spring detent arm 24 engages with the corrugated or ratchet head 27 and thereby holds the rod 18. with its release flngeris retracted against the tension of the spring 20. Surrounding the post 26 of heat conductive material, is a heater coil 28 connected in series with the electric switch 2 or otherwise connected into the electrical circuit to be controlled. In the event of overload whereby the temperature of the heater coil 28 is raised to abnormal degree, the fusible union between the corrugated or ratchet head 27 and the post 26 upon which the head is mounted is fused thereby releasing the ratchet head 27 for relative rotary motion which is effected under the influence of the expanding spring 20. This movement of the corrugated ratchet head 27 releases the detent arm 24, allowing the rod 18 and contact release finger 19to move suddenly under influence of the spring 20 thereby contacting the spring latch blade 16 to withdraw the stop shoulder 17 from engagement with the operator arm 13 which thereupon is actuated counter-clockwise as seen in Fig. 3 by the spring 14 to actuate the switch arm 10. Immediately upon cooling of the heater coil 28 and post 26, the corrugated or ratchet head 27 will be again united with the stem or post 26 by the congealing of the solder or wax. Thus the union is self healing or automatically reestablished after each operation. It is necessary, however, for the operator to reset the automatic release mechanism by depressing the rod 18 against the tension of the spring 20 until the hook detent arm 24 again engages the corrugated or ratchet head 27. Until this resetting operation is performed, the switch cannot be maintained in its closed position.

The disengagement of the stop shoulder 17 from the operator arm 13 and subsequent swinging movement of the operator arm 13 under influence of the spring 14 leaves the rock shaft 11 and detent arm 15 with its spring detent blade 16 at rest. To reset the device it is only necessary to oscillate the shaft 11 by means of the crank 12 or other actuating means, against the tension of the spring 14 until the beveled stop shoulder 17 of the spring detent blade 16 is deflected by arm 13 and again engages the same. This movement again places the spring 14 under tension. After the operator arm 13 is again interlocked with the detent arm 15 by the interengagement of the spring blade 16, the spring 14 is held under tension and such parts are freely movable to and fro as a unit by the oscillation of the shaft 11. This to and fro movement serves to correspondingly oscillate the switch arm 10 to move the switch 2 alternately into on and off positions. If the automatic release mechanism has been reset, this to and fro movement of the shaft 11 and operator arm 13 interlocked therewith against the tension of the spring 14 will serve to normally operate the switch as may be desired. However, if the resetting of the automatic release device has been neglected, the contact release arm 19 will project into the path of the spring detent blade 16 as the parts are oscillated to move the switch into closed position, and by such engagement the detent blade 16 will be flexed to withdraw the stop shoulder 17 and again release the operator arm 13 for movement under influence of the spring 14 to operate the switch. To facilitate such disengagement of the detent member 16 from the operator arm when the switch is moved to closed position, the contact release arm 19 is beveled at 19' to afford a cam surface forengagement of the extremity of the spring blade 16. Such automatic release of the operator arm and reversal of the switch threby under influence of the spring 14 will occur each time that the switch is moved to on position until the automatic device has been restored and reset by depression of the rod 18 against the tension of the spring 20 to move the contact arm 19 out of the path of the spring blade 16.

The detent arm 15 is extended beyond the shaft 11 and is adapted to make contact with the top of the housing 1 to limit the throw of the operator parts in one direction. Such engagement also forms astop abutment for the shaft 11 against which the reaction of the spring 14 is exerted to effect quick movement of the operator arm 13 when released from the detent. A stop arm 23 projecting from the top of the housing 1 arrests the movement of the operator arm 13 in the opposite direction under influence of the spring 14.

The switch 2 which may be of any suitable form and detail construction, is preferably, though not necessarily, of a double pole, single throw type. While the switch is illustrated as an oscillatory type, it is obvious that it may be a push pull, reciprocatory style or a reversible switch.

All of the electrically connected parts are mounted upon the lower section of the housing 1, within the top of which the actuator mechanism is mounted. Thus the top or closure of the housing is entirely independent and may be easily removed for inspection or repair of the parts without disturbing the electrical connections.

The insulation block 25, in which is mounted the thermal conductive post 26 carrying the ratchet head 27 also carries two terminals to which the opposite ends of the heater coil 28 are connected. One of these terminals is directly connected with the motor or other electrically operated device, the opposite side of which is connected with the switch, while the other such terminal of the heater coil is also connected with the switch.

Thus the heater coil 28 is connected in series with a motor or other electrically operated device to be protected and the two series connected devices are bridged across the switch, the opposite terminals of which are connected with the respective sides of the power line. The switch operates to open both sides of the circuit and leaves the heater coil 28 and protected device entirelyseparated from the power line.

While the construction heretofore described is the preferred commercial form of the apparatus, there is shown in Figs. 6, 7 and 8, a modified construction wherein the reversing spring is directly controlled by the thermal control device. Referring to such construction, illustrated in Figs. 6, 7 and 8, the shaft 11 carries a bifurcated operator arm 130 which is closely journaled on the shaft 11 and interlocked therewith by a spring actuated detent 30 pivoted at 31 to one side of the operator arm 130 and having an extension 30' engageable in a groove or spline 32 in a member carried by the shaft 11. This detent is spring actuated by the spring 33 into engagement with the shaft 11 whenever the extension 30 registers with the groove or spline 32 thereby locking the operator arm 130 to the shaft for unison oscillation therewith. Therefore, as the shaft 11 is oscillated to and fro during the normal manual operation the switch arm 10 and with it the switch 2 will be oscillated in unison into on and off positions. Mounted in the housing 1 at right angle to the shaft 11 is a reciprocatory rod 180 carrying a fixedly connected L-shaped extension 34. This reciprocatory rod 160 and extension 34 are subiected to retractive influence of a spring 35, one end of which is attached to the housing 1, and the other end secured to the upwardly extending arm of the L-shaped extension head 34. [A finger 36 projects laterally from the detent 30 into the path of the upwardly extending arm of the L-shaped head 34 in such relation that upon the retractive movement of the stem 180 and head 34'under infiuenee of the spring 35, the detent 30 will be 05- cillated to disengage it from the groove or spline in the shaft 11, thereby permitting the operator arm 130 and with it the switch arm 10 to be retractedby the movement of the L-shaped head 34 independently of the shaft 11. So long as the stem 160 and release head 34 are held retracted by the spring 35, the switch cannot be restored since at each oscillation of the shaft 11 and operator arm 130 necessary to return the switch arm 10, the finger 36 will contact with the upward extending arm of the head 34 toagain unlock the latch or detent 30 from the shaft 11.

Under normal operating conditions, the reciprocatory stem 180 and head 34 are held in inoperative position with the spring 35 under tension by means of a spring pawl 37 carried upon an arm 38 connected to and moving with the head 34, which pawl 37 engages with a ratchet head not shown mounted upon a stem or post 26 of heat conductive material to which it is detachably connected by a union of fusible material such as solder; wax, or similar fixative. The stem or post 26 being surrounded by the heater call 28, as before described, absorbs heat therefrom under condition of overload until the temperature rises to such degree that the fusible union between the ratchet head not shown and the post or stem 26 is broken thereby releasing the ratchet head and allowing it to turn relative to the post or stem 26 under the retractive influence of the spring 35. As the rod 180 and head 34 are retracted under influence of the spring 35, the initial action is to unlatchthe operator arm 130 from the rock shaft 11 by engagement with the lateral finger 36 of the detent 30 thereby first oscillating such detent relative to the operator arm out of engagement with the shaft 11 and upon continued movement, swinging the released operator arm 130 about the shaft 11 to effect reversal of the switch. The releasing mechanism is reset merely by pressing the stem 180 inwardly against the tension of the spring 35 until the pawl 36 again engages with the ratchet head not shown to retain the releasing device in its adjusted position.

From the above description it will be apparent that there is thus provided a device of the character described possessing the particular features of advantage before enumerated as desirable, but which obviously is susceptible of modification in its form, proportions, detail construction and arrangement of parts without departing from the principle involved or sacrificing any of its advantages.

- while in order to comply with the statute, the

invention has been described in language more or less specific as to structural features, it is to be understood that the invention is not limited to the specific features shown, but that the means and construction herein disclosed comprise the preferred form of several modes of putting the invention into effect, and the invention is therefore claimed in any of its forms or modifications within the legitimate and valid scope of the appended claims.

Having thus described our invention, we claim:

1. The combination with a manually operable switch freely movable into on and off positions, of a rotatably mounted actuator therefor adapted to automatically move the switch from on to on! position, and a thermally controlled detent moving in a direction normal to the movement of the switch adapted to release the actuator when a predetermined temperature condition has been exceeded, said detent and actuator being concentrically mounted and arranged for unison rotation when moving the switch into on and off positions.

2. The combination with a manually operable switch freely movable into on and off positions, of a thermally controlled device operative upon adjustment of the switch from off to on position for automatically returning the switch to off position under certain temperature conditions said device including an actuator moving in a direction normal to the movement of the switch and a detent engaging said actuator to move it from off to on position.

3. The combination with an electric switch manually movable into on and oil positions, of an oscillatory actuating s aft therefor, a switch operating arm carried upon the shaft for independent oscillatory movement, an actuating spring tending to move the arm independently of the shaft, a detent for interlocking the arm with the shaft against the tension of its spring, and means movable into and out of the path of the detent for disengaging the detent from the arm.

4. In a switch operating mechanism, an oscillatory operator therefor, an actuator for manually moving the operator to and fro to reverse the switch, detent means for temporarily interlocking the operator with the actuator, temperature controlled means for disengaging the detent moving in a direction normal to the movement of the operator to release the same from the manual actuator, and actuating means independently thereof for moving the operator to actuate the switch independently of the manually operable actuator.

5. The combination with an electric switch of manual actuating means therefor and automatic actuating means therefor operable independently of each other, thermally controlled means determining the operation by the respective actuating means, switch operating means normally detachably interconnected with the manual actuating means for free movement of the switch into on and off positions, and means for disengaging the switch operating means from the manual actuating means by the operation of the thermally controlled means for operation of the switch by said automatic means, and means including a member moving in a direction normal to the movement of the switch from one position to the other.

6. The combination with a switch of an oscillatory switch operator arm, a rock shaft to which the operator arm is detachably coupled for unison oscillation, an actuating spring normally under tension for oscillating the operator arm independently of the shaft, detent means for holding said spring under tension, and a thermally controlled means including a second detent having a movement for releasing the first detent to permit operative action of the spring.

7. In a device of the character described, a movable member, operable to and fro to alternate positions, a rock shaft, a rock arm loosely mounted on the shaft and having operative engagement with the movable member, an actuating springadapted to oscillate the rock arm relative to the shaft, a detent normally holding the rock arm in fixed relation with the shaft, said arm and shaft being normally freely movable to and fro in unison for to and fro adjustment of the movable member, and means for automatically disengaging the detent to permit movement of the arm under tension of the spring.

8. In a device of the character described, a member movable to alternate positions, an operator member therefor, an actuator with which the operator is detachably engageable for unison to and fro action to alternate the movable member, said actuator and operator being concentrically mounted, means for automatically disengaging the operator member from the acttuator for independent operation and motive means for the operator member when disconnected for operating the movable member independently of the actuator, said first means op erating at right angles to the movement of the operator member.

9. In a device of the character described, the combination with an alternating member to be moved, a manually operable rock shaft, an operator arm mounted thereon for relative swinging motion, detent means for detachably interconnecting the operator arm with the rock shaft for unison motion, by which the movable member is alternated, spring means for actuating the operator arm independently of the rock shaft to shift the movable member, and means for disengaging said detent to release the operator arm for action independently of the shaft.

10. In a device of the character described, actuator means for a member, including an operator manually movable to and fro for operating said member, spring means for actuating said operator in one direction, detent means for holding the actuating spring under restraint during the manual operation of the operator, and means for releasing the spring for automatic operation of the operator, said releasing means including a thermal responsive member and a detent normally held thereby.

11. In a device of the character described, a manually operable operator for a member freely movable to and fro, spring means for actuating said operator member in one direction inde pendently of its manual operation, a detent for maintaining the actuating spring under tension retaining means engaging said detent, said retaining means including a fusible member, and automatic release means therefor, including a spring actuated plunger, a trip finger carried thereby, into the path of which the detent extends when the operator is in one position of operative adjustment.

12. In an electric switch operating device of a manual actuator normally freely movable to and fro for alternating an electric switch, an operator member connecting the actuator and switch and normally moving in unison with the actuator, spring means for moving the operator member independently of the actuator to effect reversal of the switch, detent means normally restraining the spring means, and means for automatically disengaging the detent to effect reversal of the switch independently of the manual actuator, said last mentioned means including a detent biased in one direction.

13. In an electric switch operating device, an operator member normally freely movable to and fro for alternating an electric switch, spring means for actuating the operator, means for restraining the spring, and means for automatically releasing the spring upon movement of the operator in one direction to effect automatic reversal of the operator and switch in the op-- posite direction, said last mentioned means including a fusible member.

14. In an electric switch operating device, a switch operator member, manual actuating means and spring actuating means common to said actuator for independently actuating the operator to reverse an electric switch, means for normally restraining the spring actuating means whereby the operator is freely movable by said manual actuating means, and thermally con trolled means for releasing the spring actuating means for energizing the operator to shift the switch independently of the manual actuating means.

15. In an electric switch operating device, a manual actuator freely movable to and fro for alternating an electric switch, an operator member actuated thereby, spring means for automatically actuating the operator member in one direction independently of the manual actuator, restraining means for the spring means, and trip means for releasing the spring when the opera tor is in one position of adjustment whereby the operator, and with it the electric switch, will be moved to their opposite positions.

16. In an electric switch operating device, a manual actuator freely movable to and fro for alternating an electric switch, an operator member actuated thereby, spring means for automatically actuating the operator member in one direction independently of the manual actuator, restraining means for the spring means, and a trip device movable into and out of position to effect release of the said spring means, a spring actuator for said trip device, and releasible detent means normally maintaining the trip device in inoperative position.

17. In an electric switch operating device, a

spring actuated operator member, a detent therefor, an automatic trip member movable into and out of the path of said operator member detent, means for holding the trip member out of said path, and thermally controlled automatic release means for the trip member permitting its movement into operative relation with the operator detent.

18. In an electric switch operating device, a spring actuated operator, a detent therefor, a spring actuated plunger, a trip arm carried thereby adapted by its engagement therewith to disengage the operator detent and release the operator for automatic actuation of the switch, a detent carried by the plunger, a stop member engaged by the detent, and a fusible joint for the stop member adapted to release the plunger detent under abnormal temperature conditions.

19. In an electric switch operating device, a spring actuated operator, a detent therefor, a spring actuated plunger, a trip arm carried thereby adapted by its engagement therewith to disengage the operator detent and release the operator for automatic actuation of the switch, a revoluble ratchet member, a pawl carried by the plunger and engaging the ratchet member, a fusible joint for the ratchet member normally preventing rotation thereof and adapted to release the ratchet member for rotary motion to disengage the pawl under abnormal temperature conditions.

20. In an electric switch operating device, a spring actuated operator, a detent therefor, a spring actuated plunger, a trip arm carried thereby adapted by its engagement therewith to disengage the operator detent and release the operator for automatic actuation of the switch, and a fusible restraining connection for the plunger adapted to release the plunger under abnormal temperature conditions.

VICTOR L. DARNELL. MAX VOEGE.

CERTIFICATE or CORRECTION.

Patent No. 1,9.926.

July 11, 1934 VICTOR L. DARNELL, ET AL.

It is hereby certified that error appears in the printed specification of the above numbered patent requiring correction as follows: Page 3, line 59, for "closely" read loosely; page 4, line 58,- claim 5, for "and" read said; and that the said Letters Palem should be read with these corrections therein that the same may conform to the record of the case in the Patent Office.

Signed and sealed this 11th day of September, A. D. 1934.

(Seal) Leal ie Frazer Acting Commissioner of Patents. 

